DESCRIPTION (Investigator's Abstract): This proposal will study the restriction of developmental potential in the neural crest cells that form the enteric nervous system. This large and most complex division of the peripheral nervous system is derived from a small number of precursor cells that migrate along defined pathways from the vagal crest of the head and the sacral crest of the pelvis. Experiments done with previous support, in which pieces of quail gut were transplanted into appropriate or inappropriate crest migration pathways of younger chick hosts, revealed that those crest-derived cells that first colonize the gut retain a developmental potential that is greater than that which is ultimately exhibited by these cells when they differentiate within the gut. Targets reached by these transplanted cells were appropriate for the sites in which the enteric grafts were placed, and did not reflect the cell's previous history. The proposed experiments will further characterize the developmental potential of these cells by purifying them via immunoselection using a neural-crest specific antibody (NC-1) linked to magnetic beads. Experiments, which transplant these purified cells back into younger host embryos and grow them in culture, will determine: 1) whether the properties of these cells are equivalent to those that migrate out of intact gut segments; how their developmental potential changes as a function of age and of their extent of migration; and 3) whether the developmental potential of the vagal crest-derived cells is different from that of sacral crest-derived cells.